1. Field of the Invention
The present invention relates to a broadband light source unit and an optical analyzer incorporating the unit.
2. Description of the Related Background Art
A supercontinuum lightwave (SC lightwave), which is a type of broadband lightwaves, can be obtained by passing a pulse lightwave having a narrow spectral width, or the like, through a nonlinear optical medium. The lightwave broadens its spectral width through undergoing dispersion and a nonlinear optical effect in the nonlinear optical medium. Usually, the spectral width of the SC lightwave is broadened to the extent of 10 to 100 times the spectral width of the inputted pulse lightwave. The SC lightwave combines the characteristics of a white lightwave and a laser lightwave and can be produced using a relatively simple method. Consequently, the SC lightwave attracts attention as a multiwavelength light source for optical communication and as an illuminating light source for an analyzer. However, the SC lightwave has a problem in that it sometimes cannot achieve a flat spectral form. For example, the spectrum, which is supposed to be flat, is sometimes split into a plurality of portions having different wavelengths.
In view of the above circumstances, M. S. Kahn et al. have disclosed a broadband light source unit intended to flatten the spectral form of the SC lightwave in a paper entitled “Short-term spectral stability of super-continuum source using noise-like pulses generated from an EDF laser,” CLE02005, CMV5. In this light source unit, a lightwave outputted from a noise-like-mode fiber laser is introduced into a highly nonlinear fiber (HNLF). This method suppresses the spectral intensity deviation in a range of 1,200 to 1,700 nm in wavelength over the conventional SC lightwave produced by using a mode-locked actuating pulse. Nevertheless, the noise-like laser is not only limited in its applications but also disadvantageous both in cost and in reproducibility as a product.